EP3755476B1 - Flatness roller, system for measuring flatness and associated rolling operations line - Google Patents

Description

TECHNICAL AREA

The present invention relates to a flatness roller comprising a body of cylindrical shape extending along an axis of revolution and delimited radially by an outer surface. EP 3 009 206 A1 discloses a scroll according to the preamble of the rev. 1.

The invention also relates to a flatness measuring system comprising such a flatness roller, and to a line of rolling operations comprising such a flatness measuring system.

The invention applies to the field of rolling, in particular to the rolling of metal sheets such as thin metal sheets, in particular to the cold rolling of thin metal sheets. The invention also applies to the lamination of strips of paper or plastic.

PRIOR ART

It is known to use rolling to produce thin metal sheets (typically of the order of 0.1 mm to 1 mm), called “thin sheets”.

For example, in the field of packaging, the use of such thin sheets is intended to reduce the volume of waste to be recycled. In the field of transport, the use of thin sheets is motivated by a desire to reduce manufacturing costs, but also to reduce the weight of vehicles, which results in a reduction in the consumption and pollution of said vehicles.

A conventional line of rolling operations 1 is schematically illustrated by the figure 1 .

On such a line of rolling operations 1, a material 2 is conveyed, in the direction of the arrow, in the direction of a rolling stand 4. The material is, for example, a metal, paper pulp or plastic. In the rolling stand 4, the material 2 is compressed between two working rolls 6 in rotation and separated by a distance called "rolling grip". The work rolls 6 are themselves caught between two support rolls 8. The sheet 10 leaving the rolling stand 4, also called "strip", is then wound under the effect of a winder 12.

It is known that rolling, in particular the rolling of thin sheets, generally favors the appearance of defects in the flatness of the sheet 10 at the exit from the rolling mill stand 4. Such defects arise mainly from a relaxation of internal stresses due to an inhomogeneity of the forces applied by the work rolls 6, resulting from an irregularity of the grip in an axial direction of the work rolls 6, caused by elastic deformations of flattening and bending of the work rolls 6. such defects generally result from elastic deformations of flattening and bending of the rolls of the roll stand. Such deformations of the rolls of the roll stand are all the more critical as the product is thin and hard. The flatness of a rolled sheet is a fundamental quality criterion of the geometry of a rolled sheet.

It is known to implement a process for on-line monitoring of rolling operations, during which data from a system for measuring flatness at the outlet of the rolling mill stand 4 are implemented, in a regulation loop, to control nozzles 14 intended to spray rolls 6, 8 of rolling stand 4 locally to locally modify their state of deformation, or else to control actuators 16 intended to act on rolls 6, 8 of rolling stand rolling mill 4 to modify its bending, and therefore modify the distribution of force in the material 2 during rolling.

The flatness measuring system comprises, for example, a flatness roller 18.

Such a flatness roller 18 is a roller extending parallel to the work rolls 6, arranged at the outlet of the rolling mill stand 4, and against which the sheet 10 is deliberately brought into contact and in bending at an angle a, called " wrap angle, in order to generate on the flatness roller 18, by means of a tensile force on the sheet, an average force of controlled value.

Sensors fitted to the flatness roller 18 then measure a force profile applied by the strip 10 on the surface of the flatness roller 18, and more specifically along a "generatrix", which is a portion of the surface of the roller flatness roller 18 elongated along an axis parallel to the axis of the flatness roller 18.

The distribution of the differential forces on the generator, with respect to an average force, is representative of the flatness of the sheet 10. Such a distribution, called "flatness vector", constitutes the data implemented in the regulation loop previously described .

Nevertheless, the flatness rollers of the state of the art are not entirely satisfactory.

Indeed, in the case of thin sheets, the flatness rollers of the state of the art generally have a spatial resolution along each generatrix, a sensitivity, that is to say a resolution in force, a dynamic and an insufficient bandwidth to provide a sufficiently precise flatness vector to guarantee effective control by regulation of the line of rolling operations 1.

In addition, the manufacture and maintenance of such flatness rollers are generally expensive.

An object of the invention is therefore to provide a flatness roller which does not have at least some of these drawbacks.

DISCLOSURE OF THE INVENTION

To this end, the subject of the invention is a flatness roller of the aforementioned type, in which the body comprises at least one cavity extending parallel to the axis of revolution,
each cavity emerging radially on the outer surface through a plurality of slots each extending in a respective plane orthogonal to the axis of revolution, including two successive slots along an axis parallel to the axis of revolution defining between them a slat, each slat being connected to the body by two opposite circumferential ends of the slat, each circumferential end forming a recess, the slats aligned in a direction parallel to the axis of revolution forming a generatrix, the flatness roller further comprising at least one optical fiber comprising at least one deformation sensor, each deformation sensor having a measurement axis, each deformation sensor being associated with a plate, each deformation sensor being housed in a corresponding cavity and fixed to the corresponding lamella at the level of an embedding of the lamella, each deformation sensor being arranged so that the angle between the corresponding measurement axis and a plane orthogonal to the axis of revolution XX is less than or equal to 20 °, preferably less than or equal to 10°, each optical fiber being configured to receive an interrogation signal, each c deformation adaptor of each optical fiber being configured to emit, as a function of the interrogation signal received by the corresponding optical fiber, an optical response wave representative of a deformation of the deformation sensor along the corresponding measurement axis.

Indeed, the lamellae being separated by slots, the effects of the lateral couplings between lamellae are greatly reduced compared to the case where such lamellae would not be separated in the longitudinal direction.

In addition, for a given lamella, the recesses constituting the areas of the lamella which exhibit the greatest values of orthoradial deformation for a given radial force applied to the lamella, the arrangement of each deformation sensor at the level of an embedding of the lamella is the arrangement which confers the greatest sensitivity for the measurement of orthoradial deformation.

In addition, the use of a plurality of sensors arranged on the same optical fiber allows simultaneous reading of deformation for each lamella along a generatrix of the flatness roller.

Furthermore, the fact that each deformation sensor is arranged so that the angle between the corresponding measurement axis and a plane orthogonal to the axis of revolution XX is less than or equal to 20°, preferably less than or equal to 10, results in a plus large deformation of the strain sensor than in cases where the strain sensor is arranged at a higher angle, which improves the sensitivity.

Such characteristics confer sufficient sensitivity to achieve the performance required in terms of detection of gradient of deformation in the strip, typically 50 microdeformations for very thin thicknesses of strip (of the order of 0.1 mm).

• au moins une lamelle présente une épaisseur constante ;
• au moins une cavité présente, dans un plan orthogonal à l'axe de révolution, une section circulaire ;
• chaque lamelle est configurée pour présenter une déformation circonférentielle comprise entre 1 et 50 microdéformations par newton d'effort radial appliqué à la lamelle ;
• chaque génératrice présente une densité de fentes variable, la densité de fentes dans au moins une zone périphérique de la génératrice étant, de préférence, supérieure à la densité de fentes dans une zone intermédiaire de la génératrice ;
• le corps est formé d'une pluralité de tronçons agencés bout-à-bout axialement, chaque tronçon étant associé à au moins une fibre optique propre dont l'ensemble des capteurs de déformation sont fixés aux lamelles dudit tronçon ;
• le corps comporte au moins une partie pleine agencée radialement vers l'intérieur par rapport à au moins une cavité et/ou circonférentiellement entre deux cavité ;
• chaque cavité est remplie d'un élastomère agencé pour assurer une étanchéité de la cavité ;
• le rouleau de planéité comporte au moins une portion transparente, la portion transparente étant propre à transmettre au moins partiellement une onde électromagnétique appartenant à une gamme de fréquences prédéterminée ;
• chaque capteur de déformation est un réseau de Bragg photo-inscrit sur fibre.

According to other advantageous aspects of the invention, the flatness roller comprises one or more of the following characteristics, taken in isolation or in all technically possible combinations:

• at least one lamella has a constant thickness;
• at least one cavity has, in a plane orthogonal to the axis of revolution, a circular section;
• each lamella is configured to have a circumferential deformation of between 1 and 50 microdeformations per newton of radial force applied to the lamella;
• each generatrix has a variable slot density, the density of slots in at least one peripheral zone of the generatrix preferably being greater than the density of slots in an intermediate zone of the generatrix;
• the body is formed of a plurality of sections arranged axially end-to-end, each section being associated with at least one specific optical fiber of which all the deformation sensors are fixed to the slats of said section;
• the body comprises at least one solid part arranged radially towards the inside with respect to at least one cavity and/or circumferentially between two cavities;
• each cavity is filled with an elastomer designed to seal the cavity;
• the flatness roller comprises at least one transparent portion, the transparent portion being capable of at least partially transmitting an electromagnetic wave belonging to a predetermined frequency range;
• each deformation sensor is a fiber photo-inscribed Bragg grating.

Furthermore, the subject of the invention is a system for measuring flatness comprising a flatness roller as defined above and a detection unit, the detection unit being configured to emit the interrogation signal intended for each optical fiber and to receive, coming from each optical fiber, a measurement signal formed by the optical response waves generated by the optical fiber deformation sensors, the detection unit also being configured to measure an angle of rotation of the body with respect to a reference position, each generatrix being associated with a contact angle, the detection unit being configured to acquire the measurement signal coming from each optical fiber when the angle of rotation of the body is equal to l contact angle, the detection unit being further configured to calculate a flatness vector as a function of each measurement signal acquired.

• chaque génératrice est également associée à un angle en entrée de contact et un angle en sortie de contact, l'angle de contact étant compris entre l'angle en entrée de contact et l'angle en sortie de contact, l'unité de détection étant configurée pour acquérir le signal de mesure en provenance de chaque fibre optique lorsque l'angle de rotation du corps est égal à chacun parmi l'angle en entrée de contact et l'angle en sortie de contact, l'unité de détection étant, en outre, configurée pour mettre en œuvre le signal de mesure acquis pour chacun parmi l'angle en entrée de contact, l'angle de contact et l'angle en sortie de contact pour calculer un vecteur de planéité corrigé d'effets de la température sur les lamelles de la génératrice lors de la rotation du corps entre l'angle en entrée de contact et l'angle en sortie de contact correspondants ;
• le corps du rouleau de planéité est métallique et comporte un évidement central, l'unité de traitement étant au moins en partie logée dans l'évidement central.

According to other advantageous aspects of the invention, the flatness measurement system comprises one or more of the following characteristics, taken separately or in all technically possible combinations:

• each generatrix is also associated with a contact entry angle and a contact exit angle, the contact angle being between the contact entry angle and the contact exit angle, the detection unit being configured to acquire the measurement signal from each optical fiber when the angle of rotation of the body is equal to each of the contact input angle and the contact output angle, the detection unit being, in further configured to implement the measurement signal acquired for each of the contact input angle, the contact angle, and the contact output angle to calculate a flatness vector corrected for temperature effects on the slats of the generatrix during the rotation of the body between the contact entry angle and the corresponding contact exit angle;
• the body of the flatness roller is metallic and has a central recess, the processing unit being at least partly housed in the central recess.

Furthermore, the subject of the invention is a line of rolling operations comprising a system for measuring flatness as defined above.

BRIEF DESCRIPTION OF DRAWINGS

• la figure 1, déjà décrite, est une vue schématique de côté d'une ligne d'opérations de laminage ;
• la figure 2 est une représentation schématique d'un premier mode de réalisation d'un système de mesure de planéité selon l'invention, un rouleau de planéité du système de mesure de planéité étant représenté en section selon un plan contenant un axe de révolution du rouleau de planéité ;
• la figure 3 est une vue en section du rouleau de planéité de la figure 2, dans un plan orthogonal à l'axe de révolution ;
• la figure 4 est une vue de dessus d'un corps du rouleau de planéité de la figure 2, montrant une génératrice du rouleau de planéité ;
• la figure 5 est un détail de la vue en section de la figure 3 ;
• les figures 6A, 6B et 6C correspondent à la vue en section de la figure 3 lorsqu'une génératrice du rouleau de planéité se trouve respectivement à une position angulaire égale à un angle en entrée de contact prédéterminé, un angle de contact prédéterminé et un angle en sortie de contact prédéterminé ;
• la figure 7 est une représentation schématique d'un deuxième mode de réalisation d'un système de mesure de planéité selon l'invention, un rouleau de planéité du système de mesure de planéité étant représenté en section selon un plan contenant un axe de révolution du rouleau de planéité ;
• la figure 8 est une représentation schématique d'un troisième mode de réalisation d'un système de mesure de planéité selon l'invention, un rouleau de planéité du système de mesure de planéité étant représenté en section selon un plan contenant un axe de révolution du rouleau de planéité ; et
• la figure 9 est une vue en section d'une variante du rouleau de planéité de la figure 2, dans un plan orthogonal à l'axe de révolution.

The invention will be better understood using the following description, given solely by way of non-limiting example and made with reference to the appended drawings in which:

• the figure 1 , already described, is a schematic side view of a line of rolling operations;
• the figure 2 is a schematic representation of a first embodiment of a flatness measuring system according to the invention, a flatness roller of the flatness measuring system being represented in section along a plane containing an axis of revolution of the flatness roller ;
• the picture 3 is a cross-sectional view of the flatness roller of the figure 2 , in a plane orthogonal to the axis of revolution;
• the figure 4 is a top view of a flatness roller body of the figure 2 , showing a generatrix of the flatness roller;
• the figure 5 is a detail of the sectional view of the picture 3 ;
• the Figures 6A, 6B and 6C correspond to the sectional view of the picture 3 when a generatrix of the flatness roller is respectively at an angular position equal to a predetermined contact entry angle, a predetermined contact angle and a predetermined contact exit angle;
• the figure 7 is a schematic representation of a second embodiment of a flatness measuring system according to the invention, a flatness roller of the flatness measuring system being represented in section along a plane containing an axis of revolution of the flatness roller ;
• the figure 8 is a schematic representation of a third embodiment of a flatness measuring system according to the invention, a flatness roller of the flatness measuring system being represented in section along a plane containing an axis of revolution of the flatness roller ; and
• the figure 9 is a cross-sectional view of a variation of the flatness roller of the figure 2 , in a plane orthogonal to the axis of revolution.

DETAILED DISCUSSION OF PARTICULAR EMBODIMENTS

A flatness measurement system 19 according to the invention is illustrated by the figure 2 .

The flatness measuring system 19 comprises a flatness roller 18 and a detection unit 21.

The flatness roller 18 is intended to receive the metal sheet 10 (or the strip of paper or plastic) whose flatness is to be measured, and to deliver at least one measurement signal representative of the flatness of the sheet 10.

The detection unit 21 is configured to receive each measurement signal and to determine, from the measurement signal, at least one quantity relating to the flatness of the sheet 10.

The flatness roller 18 comprises a body 20, sensors 22 and two end devices 23.

The body 20 is intended to come into contact with the sheet 10 to undergo a force exerted by the sheet 10 on the body 20, when the flatness roller 18 operates within the line of rolling operations 1.

The sensors 22 are configured to measure a quantity representative of the force exerted by the sheet 10 on the body 20. As will be described later, the sensors 22 are strain sensors (also called “strain sensors ”).

The end devices 23 are, among other things, intended to support the body 20.

The body 20 will now be described with reference to the figures 2 to 5 .

The body 20 has the shape of a cylinder of revolution extending along an axis of revolution XX. As will be described later, the axis of revolution XX is also an axis of rotation of the flatness roller 18.

The body 20 is delimited radially by an outer surface 24.

The body 20 is made in one piece, or even formed of a plurality of sections integral with each other and arranged axially end-to-end.

On the example of the figure 2 , the cylinder 20 is formed by a first cylindrical section 26A integral with a second cylindrical section 26B, each having the axis of revolution XX as its own axis of revolution.

The body 20 comprises at least one cavity 28 and, for each cavity 28, a plurality of corresponding slots 30 and a plurality of corresponding slats 32. In addition, the body 20 comprises solid parts 29 arranged radially towards the inside with respect to the cavities 28 and/or circumferentially between the cavities 28.

Each cavity 28 is formed in the body 20 and opens onto the outer surface 24 through the plurality of corresponding slots 30. In addition, each strip 32 is defined between, that is to say delimited by, two slots 30 which are successive along a direction parallel to the axis of revolution X-X.

Each cavity 28 extends along a respective axis parallel to the axis of revolution X-X.

For example, the body 20 comprises four cavities 28 offset from each other in the circumferential direction of the body 20 and each extending along a respective axis parallel to the axis of revolution X-X.

Advantageously, the cavities 28 are arranged so that the center of gravity of the body 20 is on the axis of revolution XX, so that the flatness roller 18 does not present any imbalance during its rotation around the axis of XX revolution. For example, the body 20 is invariant by a rotation of a predetermined angle around the axis of revolution X-X. In this case, the cavities 28 are also invariant by said predetermined angle rotation around the axis of revolution X-X.

On the example of the picture 3 , the body 20 is invariant by a rotation of 90° (degrees) around the axis of revolution XX.

Preferably, each cavity 28 is such that, in at least one transverse plane III-III which is a plane orthogonal to the axis of revolution XX, the cavity 28 has an angular extent β, with reference to the axis of revolution XX, which is less than 180°, preferably less than 120°, for example less than 90°.

By “angular extent of the cavity 28”, it is understood, within the meaning of the present invention, the angle of the smallest angular sector formed from the axis of revolution XX and encompassing the entirety of the cavity 28. It it is, in other words, the angular sector whose two segments are tangent to the cavity 28.

For example, each cavity 28 has an angular extent β equal to approximately 40°.

Each cavity 28 emerges radially on the external surface 24 through the plurality of corresponding slots 30 .

Each slot 30 extends in a respective plane orthogonal to the axis of revolution X-X. Each slot 30 has two circumferential slot ends 31.

Preferably, two successive slots 30 along an axis parallel to the axis of revolution X-X are separated by a distance less than or equal to 50 mm, advantageously less than or equal to 25 mm, for example less than or equal to 5 mm.

Preferably, the slots 30 are identical.

Each strip 32 is axially defined between two successive slots 30 along an axis parallel to the axis of revolution X-X. In addition, each blade 32 is radially defined between the outer surface 24 and the corresponding cavity 28.

Each blade 32 comprises an outer face 34, an inner face 36 and two circumferential ends 38 opposite.

Outer face 34 is defined as a portion of outer surface 24 of body 20. Outer face 34 is convex.

The internal face 36 is oriented opposite the external face 34. The internal face 36 thus contributes to delimiting the cavity 28 corresponding to the blade 32.

Preferably, the internal face 36 is concave.

Furthermore, each blade 32 is connected to the body 20 by its two circumferential ends 38, which are defined in the axial alignment, that is to say the alignment along an axis parallel to the axis of revolution. XX, circumferential slot ends 31 of the two slots delimiting said lamella 32.

The circumferential ends 38 are also called "recesses".

For example, each lamella 32 is made in one piece with the body 20. Alternatively, each lamella 32 is attached and is fixed to the body 20 by means of its circumferential ends 38.

Advantageously, each strip 32 has a constant thickness.

By "thickness" of a lamella 32, it is understood, within the meaning of the present invention, the radial distance between the inner face 36 and the outer face 34 of the lamella 32 with respect to the axis of revolution X-X.

The thickness of the strips 32 is less than or equal to a predetermined thickness. The predetermined thickness is, in particular, chosen as a function of the mechanical properties of the sheet 10, the flatness defects of which are to be measured, as well as a desired sensitivity to stress.

The predetermined thickness is preferably less than or equal to 10 mm, advantageously less than 5 mm, for example less than or equal to 2 mm.

For example, in the case of a cavity 28 with a biconvex section, in particular an escutcheon section as on the figure 5 , the strip 32 has a constant thickness.

By "biconvex section cavity", it is understood, within the meaning of the present invention, a cavity 28 such that the intersection of a transverse plane with the cavity 28 defines a biconvex periphery, in this case convex both when the cavity is seen from an outer radial side, i.e. farther from the axis XX than the cavity, and when the cavity is seen from an inner radial side, i.e. less distant from the XX axis as the cavity.

According to another example, the cavity 28 is of circular section, as illustrated by the figure 9 .

In this case, for each slat 32, the recesses 38 correspond to the two parts of the slat 32 which are located in two angular positions located on either side of a middle part of the slat 32, with reference to the axis of revolution XX and for which the blade 32 has a maximum orthoradial deformation for a given radial force applied to the lamella 32. In this case, and as will be described later, each of the deformation sensors 22 is placed in one of the parts of the lamellae 32 likely to present a circumferential deformation at least equal to a quarter of a maximum circumferential deformation undergone by the lamella 32 during the application of a given radial force on the lamella 32, for example at least equal to half of a maximum circumferential deformation undergone by the lamella 32 during the application of a given radial force on the lamella 32.

Preferably, all the lamellae 32 of the flatness roller 18 have the same thickness.

All of the slats 32 arranged along the same axis parallel to the axis of revolution XX form a generatrix 40 of the flatness roller 18 ( figure 4 ).

For example, the generatrix 40 comprises several zones which follow one another in the direction of the axis of revolution XX and which are distinguished from each other by a density of slots 30, that is to say a number of slots 30 per unit of length along the generatrix 40. The generatrix 40 thus comprises, for example, two peripheral zones 42 separated by an intermediate zone 44.

Preferably, in the peripheral zones 42, the distance between successive slots 30 is greater than the distance between successive slots 30 of the intermediate zone 44. This gives greater measurement resolution at the level of the peripheral zones of the sheet 10, it that is to say at the edges of the sheet 10, which are areas where the internal stress gradients in the sheet 10 are the highest, and where deformations of the sheet 10 are likely to have smaller spatial extents only in an intermediate part of the sheet 10.

For example, the distance between successive slots of the intermediate zone 44 is between 10 mm and 40 mm, preferably between 15 mm and 30 mm. Furthermore, the distance between successive slots within each of the peripheral zones 42 is, for example, between 1 mm and 15 mm, preferably between 3 mm and 10 mm.

The slots of the peripheral zones 42 are preferably regularly spaced. Furthermore, the slots of the intermediate zone 44 are preferably regularly spaced.

Advantageously, the body 20 further comprises a central recess 46 ( figure 2 and 3 ).

The central recess 46 preferably extends along the axis of revolution X-X. In this case, the body 20 advantageously comprises through-openings 48 placing the central recess 46 in communication with each of the cavities 28.

In the case where the body 20 is formed of sections, the sections 26 comprise, at their ends in mutual contact, reciprocal centering means, for example a male part 50 and a female part 52 intended to cooperate with one another. other. In addition, the body 20 comprises locking means, for example a key, intended to prevent relative rotation of the sections around the axis of revolution X-X.

Sensors 22 ( figure 5 ) are configured to measure a quantity representative of a force exerted on the body 20. In particular, each sensor 22 is associated with a strip 32 and configured to measure a quantity representative of a force exerted on the corresponding strip 32.

Each sensor 22 is an optical sensor. More specifically, each sensor 22 is a segment of an optical fiber 54 in which is inscribed a Bragg grating, so that the sensor 22 is a photo-inscribed Bragg grating on fiber (also called " fiber Bragg grating " in English ). A single optical fiber 54 is capable of comprising a plurality of sensors 22, typically several tens of sensors 22.

Each sensor 22 is configured to receive, coming from an input-output end 55 of the corresponding optical fiber 54, an optical wave forming an interrogation signal.

In addition, each sensor 22 is configured to emit, in the direction of the input-output end 55 of the corresponding optical fiber 54, an optical response wave. All of the response optical waves provided by the sensors 22 form the measurement signal of the optical fiber 54.

Each sensor 22 has a respective reflection wavelength λ. Such reflection wavelength λ, also called "resonance wavelength" or "Bragg wavelength", is defined as the wavelength for which the reflection coefficient of the Bragg grating is maximal. As a result, for each optical fiber 54, the measurement signal has a spectrum comparable to a comb, each peak of the spectrum being associated with a sensor 22 of the optical fiber 54.

At a given reference temperature, when no deformation is undergone by sensor 22, the reflection wavelength of sensor 22 is called “reflection wavelength at rest” and denoted λ ₀ .

The reflection wavelengths at rest λ ₀ of the sensors 22 belonging to the same optical fiber 54 are two by two distinct.

Each sensor 22 has a measurement axis, taken as being an axis tangent to the middle of the optical fiber segment forming said sensor 22.

Each sensor 22 is such that a deformation along the corresponding measurement axis, that is to say a relative elongation (of mechanical and/or thermal origin) or a relative shortening (of mechanical and/or or thermal), results in a variation δλ of the reflection wavelength λ of the sensor 22 with respect to the reflection wavelength at rest λ ₀ . In this case, each sensor 22 is a deformation sensor.

Advantageously, for each optical fiber 54, the smallest difference between the reflection wavelengths at rest λ ₀ of the sensors 22 is strictly greater than twice the maximum variation δλ _max of reflection wavelength likely to be felt by each sensor 22.

In operation, in the measurement signal from a given optical fiber 54, each peak is associated with a sensor 22 and is located at a wavelength equal to the sum of the corresponding resting wavelength λ ₀ and of the variation δλ resulting from the deformation of the sensor 22 along the corresponding measurement axis.

Each optical fiber 54 is housed in a corresponding cavity 28, so that each sensor 22 is fixed, for example glued, to the corresponding blade 32.

More precisely, the sensor 22 is fixed to the internal face 36 of the corresponding slat 32, at the level of one of the recesses 38 of the slat 32.

More precisely, the sensor 22 is fixed to the inner face 36 of the corresponding lamella 32, in a part of the lamella 32 likely to present a circumferential deformation at least equal to a quarter of a maximum circumferential deformation undergone by the lamella 32 during the application of a given radial force on the lamella 32, for example at least equal to half of a maximum circumferential deformation undergone by the lamella 32 during the application of a given radial force on the lamella 32.

In other words, for a given radial force on the lamella 32, each point of the lamella 32 undergoes a given circumferential deformation (that is to say a circumferential displacement with respect to a situation in which no force is exerted on said slat 32). The value of this circumferential deformation is maximum for one or more particular points of the lamella 32, and is called “maximum circumferential deformation of the lamella”. The sensor 22 is fixed in a portion of strip 32 whose points, under the same conditions, undergo a deformation at least equal to half of the aforementioned maximum deformation.

Each lamella 32 is configured to present an orthoradial, that is to say circumferential, deformation of between 1 and 50 microdeformations per newton of radial force applied to the lamella 32.

By "microdeformation", it is understood, within the meaning of the present invention, a deformation corresponds to a relative elongation, that is to say a displacement relative to a base length, equal to 1.10 ^-6 .

In addition, each lamella 32 is configured to undergo an elastic deformation for any radial force whose value is between 0.1 N and 100 N. In this case, each lamella 32 is configured to present an orthoradial deformation of between approximately one microdeformation and approximately one thousand microdeformations, or even between one microdeformation and three thousand microdeformations in the case of a lamella 32 made of a high elastic limit steel.

For example, in the case of a cavity 28 with an escutcheon section, the sensor 22 is fixed to the lamella 32, away from a plane of symmetry of the lamella 32 containing the axis of revolution XX.

Furthermore, each sensor 22 is arranged so that the angle between the corresponding measurement axis and a plane orthogonal to the axis of revolution X-X is less than or equal to 20°, for example less than or equal to 10°.

By "angle between the measurement axis and the plane orthogonal to the axis of revolution XX", it is understood, within the meaning of the present invention, the smallest angle between a direction vector of the measurement axis and a vector director of a straight line belonging to said plane orthogonal to the axis of revolution XX.

Preferably, each optical fiber 54 is wound in a circular helix around an axis parallel to the axis of revolution X-X.

Advantageously, each optical fiber 54 is engaged in an associated through opening 48 so that the corresponding input-output end 55 is located in the central recess 46.

Advantageously, each cavity 28 is filled with an elastomer intended to seal the cavity 28, in particular to prevent any liquids (water, oils) from entering the cavity 28.

The elastomer is chosen so as to have an elasticity such that, for neighboring strips 32, the effect on the deformation of the strips 32 which would be due to a lateral coupling via the elastomer is negligible with regard to the sensor sensitivity 22.

Such an elastomer is, for example, a silicone elastomer.

Each side device 23 comprises a flange 56 and a bearing 58.

At least one of the two end devices 23 comprises an optical rotary joint 60. In addition, one of the two end devices 23 comprises an angular encoder 62.

Each flange 56 is arranged at a respective end of the body 20 and fixed to said end to close, preferably hermetically, the body 20.

Each bearing 58 comprises a rotor 58A, fixed to the flange 56, and a stator 58B, intended to be fixed to a frame of the rolling operations line 1, movable in rotation with respect to each other around a corresponding axis of rotation. The axis of rotation of each bearing 58 coincides with the axis of revolution XX of the body 20.

Each optical rotary joint 60, also called " fiber optic rotary joint " in English, is configured to allow uninterrupted circulation of optical waves between the flatness roller 18 and the detection unit 21, that the flatness roller 18 is in rotating (rolling operations line running) or not (rolling operations line stopped).

The optical rotary joint 60 comprises an integer number M of channels, M being equal to the number of optical fibers to which the optical rotary joint 60 is connected. For example, on the figure 2 , each optical rotary joint 60 has two channels.

Each path of optical rotary joint 60 includes a first end 60A and a second end 60B.

Each first end 60A of the optical rotary joint 60 is connected to the detection unit 21. More precisely, each first end of the optical rotary joint 60 is connected to an input-output port of a corresponding circulator.

Furthermore, each second end 60B of the optical rotary joint 60 is connected to the input-output end 55 of a corresponding optical fiber 54.

The optical rotary joint 60 is configured to receive the interrogation signal coming from the detection unit 21, and to route the interrogation signal to each optical fiber 54.

In addition, the optical rotary joint 60 is configured to receive the measurement signal from each optical fiber 54, and to route the measurement signal to the detection unit 21.

Advantageously, the optical rotary joint 60 has an IP64 or IP65 qualification, that is to say conferring total protection against dust, and protection against liquid splashes whatever their angle of incidence.

The angular encoder 62 is configured to measure an angular position of the flatness roller 18 with respect to a predetermined reference angular position.

The angular encoder 62 is connected to the detection unit 21 to transmit, to the detection unit 21, the measured angular position of the flatness roller 18.

The angular encoder 62 is advantageously of the absolute, single-turn type.

The detection unit 21 comprises an optical source 64, routing means 65, a spectral analysis module 66 and a computer 68.

The optical source 64 is configured to generate the optical wave forming the interrogation signal of the sensors 22 of each optical fiber 54.

The optical source 64 has K outputs, K being equal to the sum of the number M of channels of the optical rotary joints 60.

Each output of the optical source 64 is connected to a corresponding first end of the optical rotary joint 60. More precisely, each output of the optical source 64 is connected to an input port of the circulator associated with the corresponding first end of the optical rotary joint. 60.

Advantageously, the interrogation signal has a spectral range strictly greater than the greatest difference between the reflection wavelengths at rest λ ₀ of the sensors 22.

For example, the optical source 64 is configured to emit an interrogation signal centered around 820 nm and having, for example, a spectral range of 30 nm. In this range of wavelengths, the usual sensitivity of the sensors 22 is of the order of 0.65 μm/microdeformation. In this case, the smallest difference between the reflection wavelengths at rest λ ₀ of the sensors 22 is, for example, equal to 1.6 nm.

According to another example, the optical source 64 is configured to emit an interrogation signal whose spectrum is between 1525 nm and 1565 nm, even between 1525 nm and 1625 nm, or even between 1460 nm and 1625 nm. In this range of wavelengths, the usual sensitivity of the sensors 22 is of the order of 1.2 μm/microdeformation. In this case, the smallest difference between the reflection wavelengths at rest λ ₀ of the sensors 22 is, for example, equal to 3 nm.

Alternatively, optical source 64 is a tunable laser source.

The routing means 65 are connected to the angular encoder 62.

The routing means 65 are also optically connected to the optical rotary joint 60. In particular, the routing means 65 are connected to an output port of each circulator to receive the measurement signal coming from each optical fiber 54.

The routing means 65 are also optically connected to the spectral analysis module 66 to selectively route, to the spectral analysis module 66, the measurement signals coming from the optical fibers 54 of the same generator 40, i.e. i.e. the optical fiber or fibers 54 whose sensors 22 are fixed to the slats 32 of the generator. More specifically, the routing means 65 are configured to selectively route, to the spectral analysis module 66, the measurement signals coming from the optical fibers 54 of the same generator 40 only when the angle measured by the angular encoder 62 belongs to a predetermined range associated with said generator 40.

Preferably, the predetermined ranges are two by two disjoint.

The spectral analysis module 66 is configured to analyze, over time, the measurement signal received from each optical fiber 54.

Due to the nature of the sensors 22, the analysis by the spectral analysis module 66, at a given instant, of a measurement signal delivered by an optical fiber 54 amounts to a simultaneous analysis of the optical response waves of the set of sensors 22 belonging to the optical fiber 54.

In addition, the use of the routing means 65 is such that the spectral analysis module 66 is able to analyze simultaneously, at a given instant, the optical response waves of all the sensors 22 of a generator 40.

Furthermore, the spectral analysis module 66 is configured to deliver an analysis signal representative of the wavelength of each peak in the response signal received from each optical fiber 54. In other words, the analysis signal is representative of the spectrum of the optical wave response of each of the sensors 22 of the generator 40.

The spectral analysis module 66 is, for example, a concave grating spectrometer, associated with a matrix of photodetectors. In this case, the relative intensity between the electrical signals delivered by the photodetectors is representative of the spectrum of the measurement signal.

The computer 68 is connected to the angular encoder 62 to receive the measured angular position of the flatness roller 18.

Furthermore, the computer 68 is connected to the spectral analysis module 66 to acquire the analysis signal generated as a function of each measurement signal.

The computer 68 is configured to store, for each generatrix 40, an angle θ ₀ , called "contact angle", corresponding to a position in which the generatrix 40 is supposed to be in contact with the sheet 10, during the rotation of the roller flatness 18. In this case, the computer 68 is configured to acquire the analysis signal when the angle measured by the angular encoder 62 is equal to the contact angle θ ₀ . Such a contact angle θ ₀ is, for example, represented on the figure 6B .

For a given generatrix 40, the contact angle θ ₀ belongs to the predetermined range associated with the generatrix.

In addition, the computer 68 is configured to store, for each optical fiber 54, the reflection wavelength at rest λ ₀ of the corresponding sensors 22.

The computer 68 is also configured to determine, from the analysis signal, the reflection wavelength associated with each peak in the measurement spectrum.

The computer 68 is also configured to associate each reflection wavelength determined with the corresponding sensor 22.

For example, for each optical fiber 54, the computer 68 is configured to associate a measured wavelength with the sensor 22 which has the reflection wavelength at rest λ ₀ closest to said measured wavelength. Such an association method has a low error rate in the case where the smallest difference between the reflection wavelengths at rest λ ₀ of the sensors 22 is strictly greater than twice the maximum variation δλ _max of length d reflection wave likely to be felt by each sensor 22.

où λ_m,θ0 est la longueur d'onde mesurée lorsque l'angle mesuré par le codeur angulaire 62 est égal à l'angle de contact θ₀.In addition, the computer 68 is configured to calculate, for each sensor 22, the variation in wavelength δλ resulting from the deformation of the sensor 22 along the corresponding measurement axis, as the difference between the wavelength measured and the reference wavelength: $$\mathrm{\delta \lambda }={\mathrm{\lambda }}_{\mathrm{m},{\mathrm{\theta }}_0}-{\mathrm{\lambda }}_0$$

where λ _{m,θ 0} is the wavelength measured when the angle measured by the angle encoder 62 is equal to the contact angle θ ₀ .

• où δσ est l'effort appliqué sur la lamelle 32 (en newton N) ;
• δλ est la variation de longueur d'onde du capteur 22 (en pm) ;
• S est la sensibilité du capteur 22 (en pm/N), déterminée au cours d'une étape d'étalonnage décrite ultérieurement ; et
• C est un seuil de détection du capteur 22 (en N).

In addition, computer 68 is configured to calculate the force applied to strip 32 associated with a given sensor 22 according to the formula: $$\mathrm{\delta \sigma }=\frac{\mathrm{\delta \lambda }}{\mathrm{S}}+\mathrm{VS}$$

• where δσ is the force applied to the lamella 32 (in newton N);
• δλ is the variation in wavelength of sensor 22 (in pm);
• S is the sensitivity of sensor 22 (in pm/N), determined during a calibration step described later; and
• C is a detection threshold of sensor 22 (in N).

The determination of the detection threshold will be described later.

Preferably, the computer 68 is also configured to store, for each generatrix 40, an angle θ ⁻ , called “contact entry angle”, corresponding to a position in which the generatrix 40 is supposed not yet to have come into contact with the sheet 10, during the rotation of the flatness roller 18, as illustrated by the Figure 6A . On this Figure 6A , as well as on the figures 6B and 6C , the arcuate arrow represents the direction of rotation of the flatness roller.

Preferably, the computer 68 is also configured to store, for each generatrix 40, an angle θ ⁺ , called "contact output angle", corresponding to a position in which the generatrix 40 is supposed to no longer be in contact with the sheet. 10, upon rotation of the flatness roller 18, as illustrated by the Fig. 6C .

The contact entry angle θ ^- and the contact exit angle θ ⁺ are such that the contact angle θ ₀ is between the contact entry angle θ ^- and the contact exit angle θ ⁺ . This appears, for example, on the figures 6A to 6C .

In addition, for a given generatrix 40, the contact input angle θ ⁻ and the contact output angle θ ⁺ belong to the predetermined range associated with the generatrix.

In this case, the computer 68 is also configured to acquire the analysis signal when the angle measured by the angle encoder 62 is equal to the contact input angle θ ^- and to the contact output angle θ ⁺ , and to associate each wavelength measured by the spectral analysis module 66 with the corresponding sensor 22 .

• où λ_m,θ- est la longueur d'onde mesurée lorsque l'angle mesuré par le codeur angulaire 62 est égal à l'angle en entrée de contact θ^-; et
• λ_m,θ+ est la longueur d'onde mesurée lorsque l'angle mesuré par le codeur angulaire 62 est égal à l'angle en sortie de contact θ⁺.

In addition, the computer 68 is configured to calculate, for each sensor 22, the variation in length δλ resulting from the deformation of the sensor 22 along the corresponding measurement axis and corrected for the effects of temperature, according to the following formula: $$\mathrm{\delta \lambda }={\mathrm{\lambda }}_{\mathrm{m},{\mathrm{\theta }}_0}-\frac{{\mathrm{\lambda }}_{\mathrm{m},{\mathrm{\theta }}^{-}}+{\mathrm{\lambda }}_{\mathrm{m},{\mathrm{\theta }}^{+}}}{2}$$

• where λ _m,θ- is the wavelength measured when the angle measured by the angle encoder 62 is equal to the contact input angle θ ^- ; and
• λ _m,θ+ is the wavelength measured when the angle measured by the angle encoder 62 is equal to the angle at the contact output θ ⁺ .

For a given generatrix 40, the calculated force profile constitutes the flatness vector.

Computer 68 is also configured to compare each flatness vector to a target profile.

Advantageously, the computer 68 is also configured to generate, depending on the difference between the flatness vector and the target profile, command instructions for the nozzles 14 and/or the actuators 16.

The operation of the flatness measuring system 19 will now be described.

During an initialization step, for each optical fiber 54, the value of the reflection wavelength at rest λ ₀ of each sensor 22 of the optical fiber 54 is recorded in the processing unit 21.

In addition, for each generatrix 40, the value of the contact angle θ ₀ and, advantageously, the value of the contact input angle θ ^- and of the contact output angle θ ⁺ are recorded in the processing unit 21.

During a calibration step, a predetermined force is applied to the outer face 34 of each blade 32.

The variation of the reflection wavelength of each sensor 22 as a function of the force is measured, and a model linking said variation of the reflection wavelength to the force applied to the slat is determined. Then, the determined model is recorded in the processing unit 21. Such a model is, for example, the affine model previously described: $$\mathrm{\delta \sigma }=\frac{\mathrm{\delta \lambda }}{\mathrm{S}}+\mathrm{VS}$$

In the case where the values of the parameters of the model vary with the sensor 22, the values of the model determined for each sensor 22 are recorded in the processing unit 21 in relation to the corresponding sensor 22.

Then the flatness roll 18 is inserted into the rolling operation line 1.

The sheet 10 drives the flatness roller 18 in rotation.

The angular encoder 62 measures the angular position of the flatness roller 18.

The optical source 64 generates the interrogation signal, and the optical rotary joint 60 routes the interrogation signal to each optical fiber 54.

Each optical fiber 54 returns, to the spectral analysis module 66, the corresponding measurement signal.

When the angle measured by the angular encoder 62 belongs to a predetermined range associated with a given generatrix 40, the routing means 65 transmit, to the spectral analysis module 66, the measurement signals from the optical fibers 54 of said generator 40.

For said generator 40, the spectral analysis module 66 analyzes, over time, the measurement signal received from each optical fiber 54 corresponding. In addition, the spectral analysis module 66 delivers, over time, the analysis signal representative of the wavelength of each peak in the response signal received from each optical fiber 54.

For the contact angle θ ₀ associated with generator 40, computer 68 acquires the analysis signal. Advantageously, the computer 68 also acquires the analysis signal for the contact input angle θ ⁻ and for the contact output angle θ ⁺ associated with the generatrix 40.

Then, the computer 68 determines the current reflection wavelength for each sensor 22.

Then, the computer 68 calculates, for each sensor 22, the variation in reflection wavelength δλ associated with the current reflection wavelength λ determined, that is to say the difference between the wavelength reflection current λ determined and the reflection wavelength at rest λ ₀ .

Then, for each sensor 22, the computer 68 determines, from the reflection wavelength variation δλ calculated, the force applied to the lamella 32 associated with the sensor 22. The vector formed by the force applied to each strips 32 of generatrix 40 form the flatness vector associated with generatrix 40.

Then, the computer 68 compares the flatness vector to the target profile.

Then, the computer 68 generates, depending on the differences between the flatness vector and the target profile, command instructions for the nozzles 14 and/or the actuators 16.

The operations implemented by the spectral analysis module 66 and the computer 68, described previously, are repeated each time the angle measured by the angular encoder 62 belongs to the predetermined range associated with a new generatrix 40.

A second embodiment of the flatness measuring system 19 according to the invention is illustrated by the figure 7 .

The flatness measuring system 19 of the figure 7 differs from the flatness measuring system 19 of the figure 2 only in that it has no optical rotary joint.

In this case, the optical source 64, the routing means 65 and the spectral analysis module 66 are arranged in the central recess 46 of the flatness roller 18 to form a Bragg interrogation assembly 70.

The flatness roll 18 also includes a feed rotary joint 72, configured to provide electrical power to the Bragg interrogation assembly 70 from a source of electrical power external to the flatness roll 18.

The flatness roller 18 further comprises a rotary communication joint 74, configured to ensure communication between the Bragg interrogation assembly 70 and the computer 68, in particular to ensure the transport of the analysis signal from the module of spectral analysis 66 to computer 68.

For example, the communication rotary joint 74 is an Ethernet rotary joint.

A third embodiment of the flatness measuring system 19 according to the invention is illustrated by the figure 8 .

The flatness measuring system 19 of the figure 8 differs from the flatness measuring system 19 of the figure 7 only in that the flatness roll 18 has no feed rotary joint. In this case, a battery 76, represented schematically on the figure 8 , is arranged in the central recess 46 to supply the Bragg interrogation assembly 70 with electrical energy.

Advantageously, one of the end devices 23 of the flatness roller 18 comprises an alternator 78, electrically connected to the battery 76.

Alternator 78 is configured to convert some of the mechanical energy from the rotation of flatness roller 18 into electrical energy to recharge battery 76.

For example, the alternator 78 comprises an armature 80, integral with the body 20, and an inductor 82, intended to be fixed to the frame receiving the flatness roller 18. The armature is configured to rotate, relative to the inductor, around of the axis of revolution XX.

The inductor 82 comprises, for example, a plurality of permanent magnets. Furthermore, the armature 80 comprises, for example, a plurality of turns arranged in the magnetic field generated by the magnets of the inductor.

According to a variant of the flatness measurement systems 19 of the figure 7 Where 8 , the spectral analysis module 66 is external to the flatness roller 18. In this case, the flatness roller 18 includes an optical rotary joint which is only intended to route the response signals from the optical fibers 54 to the external 66 spectral analysis. In addition, in this case, the flatness roller 18 does not have a rotary communication joint.

According to a variant of the flatness measurement systems 19 of the figure 7 Where 8 , the flatness roller 18 has no rotary communication joint. In this case, the flatness roller 18 comprises an electromagnetic wave transmitter, configured to transmit, to the computer 68, electromagnetic waves coded by the analysis signal delivered by the spectral analysis module 66.

The computer 68 is configured to receive the electromagnetic waves emitted by the electromagnetic wave transmitter and to decode said electromagnetic waves in order to determine the reflection wavelength of each sensor 22.

In addition, the flatness roller 18 comprises at least one transparent portion in the transmission frequency range of the electromagnetic wave transmitter to allow the propagation of electromagnetic waves from the electromagnetic wave transmitter to the computer 68.

For example, the electromagnetic wave transmitter is a Wi-Fi transmitter module (IEEE 802.11 standard). For example, the transparent portion is a window formed in one of the flanges 56 of the flatness roller 18. For example, the window is made of polymethyl methacrylate (PMMA), polycarbonate (PC) or glass-epoxy composite material (also called “ glass fiber reinforced plastics ” in English).

More generally, the flatness roller 18 comprises at least one transparent portion, the transparent portion being capable of transmitting at least partially an electromagnetic wave belonging to a predetermined frequency range, for example belonging to microwaves, optical waves, near ultraviolet or near infrared.

In this case, the computer 68 is likely to be arranged in the central recess 46, so that the electromagnetic wave transmitter is used to directly transmit the command instructions for the nozzles 14 and/or the actuators 16 generated by the calculator 68.

The presence of slots 30 prevents the appearance of lateral couplings along each generatrix 40.

By "lateral coupling"(" cross-talk " in English), it is understood, within the meaning of the present application, the appearance of axial stresses along a generatrix when a radial stress is applied to the flatness roller 18. In other words, in the case of a lateral coupling, a stress applied at a given point of the generatrix 40 results in the appearance of a stress at neighboring points, in particular neighboring points belonging to the generator, even in the absence of radial force exerted on said points.

Such lateral couplings generally require heavy calculations to be compensated. In addition, the results obtained at the end of such calculations generally do not have sufficient accuracy. This results in a degradation of the performance of the regulation loop.

The presence of the slots 30 substantially reduces the propagation of axial forces along the generatrix 40. Such calculations are no longer necessary, and the performance of the regulation loop is improved.

The fact that the measurement axis of each sensor 22 forms, with any plane orthogonal to the axis of revolution XX, an angle less than or equal to 10°, leads to each sensor 22 measuring only or essentially a circumferential component, that is to say orthoradial, of the deformation of the corresponding lamella 32. However, the applicant has found that, when applying a radial force to a lamella 32, the circumferential component of the deformation of the lamella 32 is the deformation exhibiting, in absolute value, the greatest amplitude. It follows that a such an arrangement of the measurement axes of the sensors 22 maximizes the amplitude of the elongation of the sensors 22, and therefore maximizes the sensitivity of the flatness roller 18.

The use of such fiber Bragg grating sensors 22 is advantageous, insofar as their sensitivity, that is to say the amplitude of their response, for an interrogation signal of constant amplitude, is independent temperature in the usual temperature ranges in the field of rolling, in particular cold rolling.

The use of such optical sensors 22 is advantageous, in particular in a metallurgical environment, for example the steel industry, the site of electromagnetic disturbances generated by the presence of induction furnaces and rotating machines, insofar as such sensors are insensitive to such electromagnetic disturbances.

In addition, the use of such sensors 22 in association with the strips 32 gives the flatness roller 18 great sensitivity, great dynamics and great robustness. Indeed, in operation, the body 20 supports the majority of the force exerted by the sheet 10 on the flatness roller 18. In addition, such sensors 22 are likely to undergo a wide range of forces, of the order of three orders of magnitude, without risk of destruction. Furthermore, such sensors, even when they are subjected to a high average force (for example 2000 N) are capable of detecting minute variations in force (for example 2 N).

The use of such optical sensors 22 is also advantageous, insofar as the wavelength multiplexing on the same optical fiber 54 allows simultaneous analysis of the optical response waves of each sensor 22. The measurement is then synchronous on a generator, eliminating measurement bias due to unbalance phenomena, winder eccentricities, etc. This results in a substantial gain in measurement precision compared to the devices of the state of the art with electromechanical sensors, which generally require sequential acquisition and therefore do not provide a true synchronous measurement.

Such simultaneous acquisition is also advantageous insofar as a sequential acquisition of the sensors, during the rotation of the roller of flatness 18, is likely to mask potential biases linked to possible periodic force fluctuations at the level of the rolling mill stand 4.

The use of such sensors 22 is also advantageous insofar as their cost is generally lower than the cost of the usual electromechanical sensors.

The use of such optical sensors 22 is also advantageous insofar as their small dimensions allow the production of strips 32 of small axial extent, which increases the spatial resolution of the flatness measurement system 19 along each generatrix 40. This is particularly advantageous in the field of rolling thin sheets, where the axial resolution (that is to say the resolution along the axis of revolution of the flatness roller 18) required is of the order of a few millimeters, in particular at level of the side edges of the sheet 10, that is to say the edges intended to exert a force on the peripheral zones 42 of each generatrix 40.

Moreover, the use of a body 20 formed of several sections 26A, 26B allows a simpler installation of the optical fibers 54, insofar as each section 26A, 26B is capable of being equipped with the corresponding optical fibers 54, before the assembly of the body 20. Indeed, due to the dimensions of the body 20, the installation of the optical fibers 54 in a one-piece body 20 is likely to pose difficulties.

The use of a body 20 formed of several sections 26A, 26B also facilitates repairs of the flatness roller 18, insofar as only the section corresponding to a defective zone of the flatness roller 18 is replaced, and not the flatness roller in its entirety.

The presence of the solid parts 29 in the body 20 ensures that the forces exerted by the sheet metal 10 are taken up, which gives the body 20 greater rigidity than the devices of the state of the art.

In addition, the body 20 being metallic, the arrangement of all or part of the organs of the processing unit 21 (among which the optical source 64, the spectral analysis module 66 or the computer 68) in the body 20 confers to the body 20 a function of protection against electromagnetic disturbances, called "shielding" electromagnetic”. Such protection is particularly advantageous in a metallurgical environment, for example the steel industry, where electromagnetic interference is generated by the presence of induction furnaces and rotating machines.

Claims (14)

1. Flatness roller (18) including a cylindrical body (20) extending along an axis of revolution (X-X) and radially delimited by an outer surface (24),
   the body (20) including at least one cavity (28) extending parallel to the axis of revolution (X-X), characterized in that:

   each cavity (28) opens radially onto the outer surface (24) through a plurality of slots (30) each extending in a respective plane orthogonal to the axis of revolution (X-X), of which two successive slots (30) along an axis parallel to the axis of revolution (X-X) defining a lamella (32) between them,

   each lamella (32) being connected to the body (20) by two opposite circumferential ends (38) of the lamella (32), each circumferential end (38) forming a connection portion,

   the lamellas (32) aligned in a direction parallel to the axis of revolution (X-X) forming a generatrix (40),

   the flatness roller (18) further including at least one optical fibre (54) comprising at least one strain sensor (22), each strain sensor (22) having a measurement axis, each strain sensor (22) being associated with a lamella (32),

   each strain sensor (22) being housed in a corresponding cavity (28) and attached to the corresponding lamella (32) at a connection portion of the lamella (32),

   each strain sensor (22) being arranged so that the angle between the corresponding measurement axis and a plane orthogonal to the axis of revolution (X-X) is less than or equal to 20°, preferably less than or equal to 10°,

   each optical fibre (54) being configured to receive an interrogation signal, each strain sensor (22) of each optical fibre (54) being configured to send, depending on the interrogation signal received by the corresponding optical fibre (54), an optical response wave representative of a strain of the strain sensor (22) along the corresponding measurement axis.
2. Flatness roller (18) according to claim 1, wherein at least one lamella (32) has a constant thickness.
3. Flatness roller (18) according to claim 1 or 2, wherein at least one cavity (28) has, in a plane orthogonal to the axis of revolution (X-X), a circular section.
4. Flatness roller (18) according to any one of claims 1 to 3, wherein each lamella (32) is configured to have a circumferential strain between 1 and 50 microstrains per newton of radial force applied to the lamella (32).
5. Flatness roller (18) according to any one of claims 1 to 4, wherein each generatrix (40) has a variable density of slots (30), the density of slots (30) in at least one peripheral area (42) of the generatrix (40) being, preferably, greater than the density of slots (30) in the intermediate area (44) of the generatrix (40).
6. Flatness roller (18) according to any one of claims 1 to 5, wherein the body (20) consists of a plurality of sections (26A, 26B) arranged axially end to end, each section being associated to at least one specific optical fibre (54) whereof all of the strain sensors (22) are attached to the lamellas (32) of said section (26A, 26B).
7. Flatness roller (18) according to any one of claims 1 to 6, wherein the body (20) includes at least one solid portion (29) arranged radially inwardly in relation to at least one cavity (28) and/or circumferentially between two cavities (28).
8. Flatness roller (18) according to any one of claims 1 to 7, wherein each cavity (28) is filled with an elastomer arranged to provide a sealing of the cavity (28).
9. Flatness roller (18) according to any one of claims 1 to 8, including at least one transparent portion, the transparent portion being suitable for transmitting at least partially one electromagnetic wave belonging to a predetermined range of frequencies.
10. Flatness roller (18) according to any one of claims 1 to 9, wherein each strain sensor (22) is a fibre Bragg grating.
11. System for measuring flatness (19) including a flatness roller (18) according to any one of claims 1 to 10 and a detection unit (21),

    the detection unit (21) being configured to send the interrogation signal to each optical fibre (54) and to receive, from each optical fibre (54), a measurement signal formed by the optical response waves generated by the strain sensors (22) of the optical fibre (54),

    the detection unit (21) being further configured to measure an angle of rotation of the body (20) in relation to a reference position, each generatrix (40) being associated with a contact angle (θ₀),

    the detection unit (21) being configured to acquire the measurement signal coming from each optical fibre (54) when the angle of rotation of the body (20) is equal to the contact angle (θ₀),

    the detection unit (21) being further configured to calculate a flatness vector depending on each acquired measurement signal.
12. System for measuring flatness (19) according to claim 11, wherein each generatrix (40) is also associated with an entry contact angle (θ^-) and an exit contact angle (θ⁺), the contact angle (θ₀) being between the entry contact angle (θ^-) and the exit contact angle (θ⁺),

    the detection unit (21) being configured to acquire the measurement signal coming from each optical fibre (54) when the angle of rotation of the body (20) is equal to each of the entry contact angle (θ^-) and the exit contact angle (θ⁺),

    the detection unit (21) being, furthermore, configured to implement the measurement signal acquired for each of the entry contact angle (θ^-), the contact angle (θ₀) and the exit contact angle (θ⁺) in order to calculate a flatness vector corrected with effects of the temperature on the lamellas (32) of the generatrix (40) during the rotation of the body (20) between the corresponding entry contact angle (θ^-) and the exit contact angle (θ⁺).
13. System for measuring flatness (19) according to claim 11 or 12, wherein the body (20) of the flatness roller (18) is metal and includes a central recess (46), the processing unit (21) being at least partially housed in the central recess (46).
14. Rolling operation line (1) including a system for measuring flatness (19) according to any one of claims 11 to 13.

Images